struct.unpack on 64-bit platforms

[Nadav Samet]

Hi,

I am trying to unpack a 32-bit unsigned integer from a string using
struct.unpack.
so using string.unpack(' L', data) would work fine on 32-bit systems,

But apparently, on 64-bit platforms it tries to read 64-bit unsigned
integer (since
that's what the C Type unsigned long means on 64-bit platforms).

So what's the way to make it read exactly 32-bits, on all platforms?

Thanks,
Nadav

[Georg Brandl]

Re: struct.unpack on 64-bit platforms

Nadav Samet wrote:[color=blue]
> Hi,
>
> I am trying to unpack a 32-bit unsigned integer from a string using
> struct.unpack.
> so using string.unpack(' L', data) would work fine on 32-bit systems,
>
> But apparently, on 64-bit platforms it tries to read 64-bit unsigned
> integer (since
> that's what the C Type unsigned long means on 64-bit platforms).
>
> So what's the way to make it read exactly 32-bits, on all platforms?[/color]

Looking into the docs, prepending your format string with "=" should
make "L" exactly 32 bits on each platform.

Georg

[Jorgen Grahn]

Re: struct.unpack on 64-bit platforms

On 22 Jun 2006 09:30:26 -0700, Nadav Samet <thesamet@gmail .com> wrote:
....[color=blue]
> But apparently, on 64-bit platforms it tries to read 64-bit unsigned
> integer (since
> that's what the C Type unsigned long means on 64-bit platforms).[/color]

On /some/ 64-bit platforms. Others let unsigned long be 32-bit and introduce
the 64-bit 'long long' types (and 64-bit pointers).

The term "64-bit", like "32-bit" before it, is too vague to use in technical
discussions, IMHO.

/Jorgen

--
// Jorgen Grahn <grahn@ Ph'nglui mglw'nafh Cthulhu
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